Active mining operations often still build similar systems because the technology is well understood and because the mining companies must comply with effluent standards or face stiff fines. Passive technologies are still relatively experimental. However, the science of passive treatment is becoming better understood, and the passive treatment system do not fail catastrophically. If power is lost to an active treatment site, or if a company goes bankrupt, active treatment stops.
Map view diagram of the Rausch Creek Mine Drainage Treatment Facility
Except at very high flows, all of Rausch is diverted into the facility. Ca(OH)2 is added as a slurry at the flash mixer, and air is added in the oxidation tanks. There are two clarifiers which are followed by single thickener. The slurry from the bottom of the thickener is pumped either to the sludge holding tanks or to a belt filter press. The sludge is transported to a nearby mine strip pit for disposal. Water from the top of the clarifiers flows by gravity to the polishing ponds. The downstream polishing pond holds brown trout.
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